The object of this study is to determine if CP 99994, a Substance P receptor antagonist, results in altered kinetics of synovial fluid movement in rheumatoid arthritis. MRI imaging with the imaging agent gadolinium is used. Secondary goals are to determine the pharmacodynamic relationships of gadolinium movement into synovial fluid space with dose and serum levels of CP 99994 and to determine if this drug reduces joint pain and swelling.